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Chapter 37 Output Compare
7.Q & A
7.11 How do I enable interrupts?
Enabling of interrupts is done with interrupt request permission bit (OCS01. ICE[1:0]), (OCS23. ICE[1:0]),
(OCS45. ICE[1:0]), (OCS67. ICE[1:0]).
Interrupt requests are cleared with interrupt request bits (OCS01. ICP[1:0]), (OCS23. ICP[1:0]), (OCS45.
ICP[1:0]), (OCS67. ICP[1:0]).
7.12 Compare value calculation procedure
• Toggle output pulse
(Example) To output a period: A, phase difference 1/4 phase pulse
Formula:Compare 0 value = (A/2) / count clock
Compare 1 value = (A/4) / count clock
(Count clock: time set with free-run timer)
Note: To clear free-run timer 2 on compare 0 match setting (TCCS2.MODE=“1”) and CMOD=“0” setting are necessary.
Calculation example: A=1024us, count clock =125ns
Compare 0 value = (1024000 / 2) / 125 - 1 = 4095 = FFFh
Compare 1 value = (1024000 / 4) / 125 - 1 = 1023 = 7FFh
• PWM output
(Example) To output a period: A, duty 1/4 - 3/4 (“L”) PWM,
Formula: Compare 0 value = A / count clock
Compare 1 value = (A/4) / count clock (when duty 1/4)
(A x 3/4) / count clock (when duty 3/4)
(count clock: time set with free-run timer)
Note: To clear free-run timer 0 on compare 0 match setting (TCCS0.MODE=“1”) and CMOD=“1” setting are necessary.
Calculation example: A=1024us, count clock =125ns
Compare 0 value = 1024000 / 125 - 1 = 8191 = 1FFFh
Compare 1 value = (1024000 / 4) / 125 - 1 = 1023 = 7FFh (when duty 1/4)
(1024000 x 3 / 4) / 125 - 1 = 1023 = BFFh (when duty 3/4)
Interrupt request permission bit (ICE0, ICE1)
Interrupt disabled Set to “0”
Enable interrupts Set to “1”
Interrupt request bit (ICP0, ICP1)
Interrupt request clear Write “0”
OP0
OP1
1/4
A
OCU0
OCU1
Phase difference 1/4
A
OP1
1/4-3/4
A
OCU1
1/4-3/4
A